The present invention relates to isolator systems and, in particular, to management of refresh signaling in isolator systems.
Isolators are devices that exchange data signals between two galvanically isolated circuit systems. The circuit systems each operate in different voltage domains, which may include different source potentials and different grounds. Isolation devices may provide data exchange across an isolation barrier, which maintains the galvanic isolation. Typical isolation devices include micro-transformers, capacitors, magneto-resistors/giant magneto-resistors and opto-electronic devices.
A variety of signaling protocols have been developed for isolator systems. Many involve transmitting predetermined types of signals across the isolator device in response to predetermined events in an input signal. For example, rising and falling edges in a binary input signal might be transmitted respectively as a single pulse and a pair of pulses. Alternatively, the rising and falling edges in the input signal might be transmitted respectively as a pulse of positive polarity and a pulse of negative polarity. Additionally, many isolator systems transmit “refresh signals” across the isolator device when there has been no change in the input signal for a predetermined period of time. These refresh signals are transmitted across a common isolator device as the signal pulses that are generated in response to transitions in the input signal.
This signaling scheme can be problematic in some circumstances. When a refresh pulse is followed very quickly by a transition in an input signal, the resulting signal pattern can be misinterpreted at a receiver. Some isolator systems include provisions to guard against such collisions but increase propagation delay in signal transfer across an isolator device, which is disadvantageous. Accordingly, the inventor perceives a need in the art for an isolator system that protects against collisions between refresh signals and data-induced transmission signals in an isolator without associated penalties.